When manufacturing stimulable (storage) phosphor plates for digital imaging, all parameters are controlled with the highest care possible, as images should be obtained with the best information possible, i.a. an optimized signal to noise ratio. One of the most important factors related with that signal to noise ratio is speed (sensitivity) of the storage phosphors in the storage phosphor plate or panel.
A higher speed stands for detection of higher amounts of photons by the photomultiplier. Noise is directly related with the number of detected quanta and is proportional therewith.
Speed of a plate or panel for computed radiography, also called CR, is determined by the number of emitted photons per dose unit, set free by photostimulation of energy, stored in the stimulable phosphors after exposure to X-rays.
Improving speed for X-rays of imaging plates by heat treatment has already been described before in literature: such a treatment, known as “annealing” e.g. by heating during a time between 10 minutes and 15 hours at a temperature between 80 and 220° C. as exemplified in EP-A 1 217 633, requires quite a lot of time and such an application demands presence of heat resistant substrates as it should withstand at least such high temperatures, set forth.